Danny Garcia won the vacant WBC welterweight title with a unanimous points decision over fellow American Robert Guerrero in Los Angeles.
Garcia started slowly but controlled the later rounds to win a world title in only his second bout at 147lb.
The belt became vacant when Floyd Mayweather retired last year.
Garcia, who is unbeaten in 32 professional fights, knocked out Amir Khan in 2012 and the Briton says he is keen on a rematch.
Khan, who attended the Garcia-Guerrero fight at the Staples Center, was expected to fight compatriot and IBF welterweight champion Kell Brook in the summer but negotiations have stalled.
Khan, 29, is the mandatory challenger for Garcia's WBC belt but the champion's father and trainer, Angel Garcia, says they are not interested in a return match.
Guerrero, a former three-weight world champion, got off to an impressive start against Garcia but became less mobile and less effective as the fight wore on.
The 27-year-old Garcia eventually worked his way into the contest, exploiting Guerrero's lack of head movement and porous defence.
The bout turned when Guerrero rocked Garcia with a straight left in the fifth round, before Garcia answered with a series of punishing right hands in the sixth.
All three ringside judges scored the fight 116-112 in Garcia's favour, condemning 32-year-old Guerrero to his fourth defeat in 38 fights and his third in his past five.
"I'm back where I belong," said Garcia. "I knew I would win at least eight or nine rounds."
Guerrero said: "Not one person out there thought Danny won, apart from his team. I pressured him. I nailed him, busted his body up. I definitely want a rematch."
Infighting between promoters threatens to nix some of the most compelling contests in a vibrant welterweight division.
Bob Arum promotes former six-weight world champion Manny Pacquiao and WBO champion Timothy Bradley, who fight next month; Al Haymon manages Garcia, WBA champion Keith Thurman and former IBF champion Shawn Porter, who fight in March.
Intriguingly, Haymon also advises Khan - but with Angel Garcia saying his son would like a unification match next, Brook would also appear to be in the running.